In the field of compression-ignition internal combustion engines (diesel engines), in particular, the continuous tightening of limit values for pollutant emissions therefore results in stricter requirements with respect to particulate and nitrogen oxide (NOx) emissions.
The formation of nitrogen oxides may be reduced in this case with the aid of so-called exhaust gas recirculation (EGR) and by changing the point in time of a fuel metering into a combustion chamber of the internal combustion engine, e.g. by delaying the beginning of a fuel metering or a corresponding fuel injection. In the case of a so-called common rail system (CRS) including a high pressure accumulator for fuel, the nitrogen oxide formation may also be reduced by lowering the rail pressure.
The active principle underlying the aforementioned measures is based, in particular, on lowering the combustion temperature in the aforementioned combustion chamber. The aforementioned measures may also result in disadvantages due to the influencing of the combustion process. In this way, on the one hand, an increase in fuel consumption may occur due to reduced combustion efficiency.
On the other hand, due to the resultant lower combustion efficiency, the particulate emissions may increase in the case of a compression-ignition internal combustion engine (diesel engine). As a result, in the case of such an internal combustion engine, NOx emissions, increased fuel consumption, as well as particulate emissions, present conflicting objectives.
All aforementioned measures (delayed combustion position, reduced rail pressure) tend to result in reduced noise generation, the noise generation being additionally influenceable by the timing and quantity of the pre-injections.
Due to the previous statutory requirements for the exhaust-gas test cycle in the passenger car sector, there are only low requirements on the reduction of pollutant emissions during the dynamic operation of the internal combustion engine. In order to optimize a corresponding injection system, efforts were essentially concentrated on reducing emissions in conjunction with good consumption values and acceptable noise development under stationary conditions (i.e., no load changes, only moderate acceleration, etc.). In particular, setpoint values for injection parameters are determined in this case on the basis of a stationary characteristic map and based on the speed and the load of the internal combustion engine.
Furthermore, exhaust gas aftertreatment systems for NOx reduction are known, e.g., an NOx storage catalyst (NSC), a catalyst having selective catalytic reduction (SCR), or a particulate filter including an SCR coating (SCRF), which are referred to in general as NOx exhaust gas aftertreatment systems which either temporarily store raw NOx emissions resulting from combustion and break down the emissions into non-harmful products during a so-called regeneration phase (NSC) or provide for an immediate conversion into non-harmful products by way of the addition of reducing agents (SCR). The efficiency of an NOx exhaust gas aftertreatment system which is achievable, in principle, in this case, is dependent on further limiting conditions, however, such as, e.g., the size of the catalytic converter, the material of the particular catalytic converter, the mass flow rate of the NOx, the exhaust gas temperature, the composition of the exhaust gas, the loading state of the catalytic converter (NSC), or the fill level of the reductant (SCR) and, therefore, is frequently not optimal.
In exhaust-gas investigations with respect to the aforementioned combustion-related emissions of an internal combustion engine affected here, highly dynamic test cycles or test cycles including a substantially greater dynamic portion (i.e., load jumps or rapid load increases, in particular) are now also being carried out or will also be carried out in the future due to statutory requirements for passenger car engines and commercial vehicle engines with respect to the aforementioned measurements carried out during the purely static operation of an internal combustion engine. The focus in this case, in particular, is on so-called “real driving emissions” (RDE) in Europe, Japan, and the USA. In this case, fuel consumption will also be the focus of a corresponding certification.